Heretofore, it has been known that the braking of vehicles may be achieved by the transmission of brake force by means of an hydraulic system. While such systems have generally been satisfactory, it is known that there are numerous inherent drawbacks with such systems, particularly with respect to their utilization in aircraft. Obviously, such systems are susceptible to leaks which may, and often do, result in a diminution of braking efficiency. The leaks further tend to allow hydraulic fluid to spread over other elements of the aircraft, thereby collecting undesirable dirt, dust, and the like. Should hydraulic fluid actually reach the disks of the brake disk stack, adverse effects on braking efficiency would result.
It is further known that hydraulic braking systems greatly add to the weight of the aircraft, a most undesirable feature. Further, such systems inherently include an hydraulic lag period between the impulse at the brake pedal and the response at the brake disk. Such a delay in brake signal propagation is, of course, undesirable where aircraft are required to land on runways of fixed length and under all types of adverse weather conditions. In general, the maintenance of hydraulic braking systems has been found to be exceptionally costly and time-consuming.
Electric brake mechanisms have been known in the art by virtue of at least the embodiments presented in U.S. Pat. No. 4,432,440, assigned to Goodyear Aerospace Corporation, the assignee of the invention herein. Suffice it to say for an understanding of the instant application, electric brakes typically utilize one or more reversible electric motors operating in conjunction with a brake disk stack to selectively achieve either engagement or release of the alternately rotating and stationary disks of the stack. Of course, engagement achieves a braking effect, while disengagement results in a release of brake torque.
The instant invention presents a control circuit adapted for implementation with the reversible motors of an electric brake system to achieve the desired application and release of brake torque. While the invention is described with respect to implementation in the braking system of an aircraft, it should be understood that the invention is applicable to braking systems for numerous types of vehicles.